1. Field of the Invention
The invention relates to an image-capturing device, more particularly to a thin image-capturing device for forming an image of an uneven surface of an object.
2. Description of the Related Art
In U.S. Pat. No. 5,621,516, there is disclosed an optical device for forming an image of an uneven surface. The optical device includes a plane-parallel plate with a pair of parallel plane surfaces and made of a transparent material having a refractive index larger than that of water. An object having an uneven surface, such as a finger, is placed in close contact with one of the plane surfaces of the plane-parallel plate. A light source illuminates the object through the other one surface of the plane-parallel plate. When light rays are scattered back into the plane-parallel plate by the uneven surface of the object and are totally reflected at the other one of the plane surfaces of the plane-parallel plate, only light rays totally reflected at an angle larger than a critical angle are received by an image-capturing device.
In U.S. Pat. No. 6,657,185, there is disclosed an uneven pattern detector that includes first and second optical systems, and a transparent light guide body. The first optical system has a light source. The light guide body has an incident face receiving incident light from the light source, a detection face facing the incident face for placing of a subject having an uneven pattern, a curved surface reflecting scattered light from the detection face, and an optical surface facing the curved surface and having an opening outputting light reflected from the curved surface. The second optical system, such as an imaging lens, guides the light from the opening of the optical surface to a camera device.
In the aforementioned conventional devices, the light source is disposed opposite to the surface where the target object or subject is to be placed. This results in a relatively thick size for the aforementioned conventional devices. It is thus desirable to further reduce the size of the aforementioned devices to meet current trends toward miniaturization for application in portable electronic devices.